Living things have certain life processes in common. There are seven things that they need to do to count as being alive. The phrase MRS GREN is a way to remember them:
|M||Movement||All living things move, even plants|
|R||Respiration||Getting energy from food|
|S||Sensitivity||Detecting changes in the surroundings|
|G||Growth||All living things grow|
|R||Reproduction||Making more living things of the same type|
|E||Excretion||Getting rid of waste|
|N||Nutrition||Taking in and using food|
It can be easy to tell if something is living or not. A teddy bear might look like a bear, but it can't do any of the seven things it needs to be able to do to count as being alive.
What about a car? A car can move, it gets energy from petrol (like nutrition), it might have a car alarm (sensitivity), and it gets rid of waste gases through its exhaust pipe (excretion). But it can't grow or make baby cars. So a car is not alive.